获取0到1的随机数

double X=((double)rand()/(double)RAND_MAX);

 1 #include <iostream>
 2 #include <iomanip>
 3 #include <map>
 4 #include <random>
 5 
 6 int main()
 7 {
 8     std::random_device rd;
 9 
10 
11     std::mt19937 e2(rd());
12 
13     std::uniform_real_distribution<> dist(0, 1);
14 
15     std::map<int, int> hist;
16     for (int n = 0; n < 10000; ++n) {
17         ++hist[std::round(dist(e2))];
18     }
19 
20     for (auto p : hist) {
21         std::cout << std::fixed << std::setprecision(1) << std::setw(2)
22                   << p.first << ‘ ‘ << std::string(p.second/200, ‘*‘) << ‘\n‘;
23     }
24 }

1 #include <stdlib.h>
2 
3 double randZeroToOne()
4 {
5     return rand() / (RAND_MAX + 1.);
6 }

double randMToN(double M, double N)
{
    return M + (rand() / ( RAND_MAX / (N-M) ) ) ;  
}